This project represents further efforts to elucidate the etiology of high incidence of Amyotrophic Lateral Sclerosis (ALS) and Parkinsonism Dementia (PD) on the island: of Guam. A patient-control prospective study (Registry) was established in 1958. The initial analysis of the Registry data published in 1967 and the follow up,, analysis published in 1986 showed that these diseases as found on Guam are highly' familial. That is, relatives of patients have a higher risk for developing the disease than those of controls. The next question to be answered is whether this familial occurrence is due to genetic or environmental factors. The specific objectives of this study are: A) To ascertain the extent of genetic involvement in the high incidence of Amyotrophic Lateral Sclerosis and Parkinsonism Dementia through: (1) segregation, analysis of the pedigrees of all patients diagnosed since 1958 and, (2) through segregation analysis of sibships where both parents, one parent or neither of the parents (controls) are affected with ALS and PD. B) To study the distribution of various established genetic and anthropological markers among the normal Guamanian populations and compare them with those of the ALS and PD patients. C) To ascertain the effects of immobilization due to paralysis on bone density.